Aspects of the present disclosure relate generally to wireless communications and, more particularly, to a method and an apparatus for regaining service by selecting a detected cell not included in a neighbor cell list (NCL).
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
3rd Generation Partnership Project (3GPP) standards have specified rules and methods for handling idle mode cell camping, selection, and/or reselection in TS 25.133 and TS 25.304 (both of which are hereby incorporated by reference in their entirety). As per the specifications, a user equipment (UE) should move to a highest “ranked” cell that is part of a signaled neighbor cell lists (NCL) when the UE is having difficulty communicating with its current serving cell. More particularly, when the UE is in a relatively poor radio frequency (RF) scenario, e.g., its current serving cell is weak and it cannot find a neighbor cell that is stronger, the specification prescribes that the UE should report its out-of-service status to higher layers once the UE has failed cell selection criteria (S-criteria) for 12 seconds. The S-criteria is fulfilled when Srxlev>0 and Squal>0, where Srxlev is a cell selection receive level value in decibels (dB) and Squal is a cell selection quality value in decibels (dB).
Upon declaring out-of-service status, the standards prescribe that the UE camp on a new cell as soon as possible. To accomplish this, the UE scans all supported frequency bands to find the best cell it can camp on. However, this frequency scan is costly in terms of duration and power consumed and may cause an undesirable delay in re-establishing connection.
As such, improvements in acquiring service upon determining that a UE has an out-of-service status are desired.